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add get_state_root helper

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Danny Ryan 2019-03-04 11:45:41 -07:00
parent 5ac30fdf77
commit a561656b68
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1 changed files with 14 additions and 2 deletions
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specs/core/0_beacon-chain.md
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@ -72,6 +72,7 @@
- [`get_next_epoch_committee_count`](#get_next_epoch_committee_count) - [`get_next_epoch_committee_count`](#get_next_epoch_committee_count)
- [`get_crosslink_committees_at_slot`](#get_crosslink_committees_at_slot) - [`get_crosslink_committees_at_slot`](#get_crosslink_committees_at_slot)
- [`get_block_root`](#get_block_root) - [`get_block_root`](#get_block_root)
- [`get_state_root`](#get_state_root)
- [`get_randao_mix`](#get_randao_mix) - [`get_randao_mix`](#get_randao_mix)
- [`get_active_index_root`](#get_active_index_root) - [`get_active_index_root`](#get_active_index_root)
- [`generate_seed`](#generate_seed) - [`generate_seed`](#generate_seed)
@ -941,6 +942,17 @@ def get_block_root(state: BeaconState,
`get_block_root(_, s)` should always return `hash_tree_root` of the block in the beacon chain at slot `s`, and `get_crosslink_committees_at_slot(_, s)` should not change unless the [validator](#dfn-validator) registry changes. `get_block_root(_, s)` should always return `hash_tree_root` of the block in the beacon chain at slot `s`, and `get_crosslink_committees_at_slot(_, s)` should not change unless the [validator](#dfn-validator) registry changes.
### `get_state_root`
```python
def get_state_root(state: BeaconState,
slot: Slot) -> Bytes32:
"""
Return the state root at a recent ``slot``.
"""
assert slot < state.slot <= slot + SLOTS_PER_HISTORICAL_ROOT
return state.latest_state_roots[slot % SLOTS_PER_HISTORICAL_ROOT]
```
### `get_randao_mix` ### `get_randao_mix`
```python ```python
@ -1674,9 +1686,9 @@ At every `slot > GENESIS_SLOT` run the following function:
def advance_slot(state: BeaconState) -> None: def advance_slot(state: BeaconState) -> None:
state.latest_state_roots[state.slot % SLOTS_PER_HISTORICAL_ROOT] = hash_tree_root(state) state.latest_state_roots[state.slot % SLOTS_PER_HISTORICAL_ROOT] = hash_tree_root(state)
state.latest_block_roots[state.slot % SLOTS_PER_HISTORICAL_ROOT] = get_block_root(state, state.slot - 1) state.latest_block_roots[state.slot % SLOTS_PER_HISTORICAL_ROOT] = get_block_root(state, state.slot - 1)
if state.latest_block_header.state_root == ZERO_HASH:
state.latest_block_header.state_root = get_state_root(state, state.slot)
state.slot += 1 state.slot += 1
if state.latest_block_header.state_root == ZERO_HASH:
state.latest_block_header.state_root = get_state_root(state, state.slot - 1)
``` ```
### Per-block processing ### Per-block processing